It is desirable in a future mobile communication system to alleviate human participation in planning, operating and maintaining a network by introducing a network self-optimization mechanism in which the network optimizes a parameter automatically according to a statistic to reduce the cost of building and operating the network. At present it is desirable to adopt an approach in which UEs could be configured by the network to report something for the purpose of alleviating the workload of a manual drive test. On the other hand, it is also desirable to obtain radio measurement information of an area inaccessible to a normal manual drive test.
As ascertained in the R10 protocol of the Long Term Evolution (LTE) system, the architecture of applying the control plane is adopted for a Minimization Drive Test (MDT), and this architecture is advantageous in that an evolved base station (base station) can control a UE accurately. The architecture of applying the control plane has to adopt Radio Resource Control (RRC) signaling to bear parameters with which the UE is configured by the network and information reported from the UE to the network. The RRC signaling has to be encrypted and integrity-protected by a Packet Data Convergence Protocol (PDCP) layer.
MDT measurement is divided into Immediate MDT measurement and Logged MDT measurement particularly as follows:
In Immediate MDT measurement, a UE measures and reports an MDT in a connected mode. Reuse the form of Radio Resource Management (RRM) measurement, a report is sent to the base station/RNC once a report condition is satisfied.
In Logged MDT measurement, a UE measures an MDT in an idle mode and reports the MDT in a subsequent connected mode. The measurement result will be obtained and stored in the UE once a configured trigger condition is satisfied and will be reported to the base station/RNC in a subsequent appropriate occasion.
A log configuration of an MDT is transmitted from the network to a UE in a connected mode, using a new configuration method instead of extending the existing RRM measurement. Specifically:
At the UE side, when the RRC connection is released, the UE will not release the received MDT log configuration but still store it, start MDT measurement and collect a measurement result in an idle mode.
At the network side, when the RRC connection is released, the network will neither store the information on an MDT context for a logged MDT nor transport the MDT context between the network nodes. The MDT context stored at the network side will be released together with the RRC connection.
In the case of a logged MDT, a UE will report a log available indicator to the network side in RRC signaling if the UE enters a connected mode or moves to a new cell when the UE has an available log. Taking an LTE system as an example, FIG. 1 illustrates an RRC connection setup procedure.
Upon successful setup of an RRC connection, a UE will transmit an RRC Connection Setup Complete message to the network side, where the message carries an indicator of whether the UE stores an available log. Subsequently upon reception of the indicator the network side can request the UE to report a stored log result of an MDT measurement.
Alike in LTE handover and reestablishment procedures, a UE will transmit a log available indicator to a handover target cell/a reestablished cell to indicate the presence of a log result available to the new cell if the UE stores the log result.
In a Universal Mobile Communication System (UMTS), a UE will also transmit a log available indicator to an updated target cell if a relocation procedure of a Serving Radio Network Subsystem (SRNS) takes place.
The following seven measurement items to be measured by a UE are defined for existing MDT measurement:
A Periodical downlink pilot measurement, a Serving Cell becoming worse than a threshold, a transmit power headroom becoming less than a threshold, a Random access failure, a Paging Channel Failure, a Broadcast Channel failure and a Radio link failure report.
Besides the foregoing seven measurement items, addition of other measurement items, e.g., a measurement item related to a Quality of Service (QOS) of a UE, will not be precluded in a subsequent standardization process. If several of these measurement items are used for an immediate MDT in a connected mode, then a configuration of these measurements is transmitted at the network side, and thus the UE will monitor them in a connected mode and still reuse a report message, used for an RRM measurement, for a report to the network side when an event is triggered.
The inventors have identified the following technical problems in the prior art during making of the invention:
A report of MDT measurement result data of a UE is borne over a Signal Radio Bearer 2 (SRB2), and a problem will occur with the report if the size thereof exceeds a range that can be accommodated by a PDCP module: the PDCP module can not support RRC signaling with a large amount of data and thus can not apply subsequent security protection and transmit the signaling to an underlying layer for reporting, thus resulting in a failure of reporting the MDT measurement result data.